Answer:
Explanation:
Molarity is the number of moles or grammes of a substance present in one dm³ of a solution. Molarity is often expressed in the unit of moldm⁻³.
Molarity = [tex]\frac{concentration}{Molar mass of substance}[/tex]
Molarity = [tex]\frac{number of moles }{Volume}[/tex]
(a) 293 gram HCL in 666 ml of solution, a concentrated HCL solution
We are given:
Mass of HCl = 293g
Volume of solution = 666ml
Unknown:
Molarity of HCl
Let us convert the volume into dm³:
1000mL = 1dm³
666mL = [tex]\frac{666}{1000}[/tex] dm³ , 0.666dm³
Now, we solve for molarity:
Molarity = [tex]\frac{number of moles }{volume}[/tex]
The number of moles is unknown and can be derieved from the equation below:
Number of moles of HCl = [tex]\frac{mass}{molar mass}[/tex]
Molar mass of HCl = 1 + 35.5 = 36.5gmol⁻¹
Number of moles of HCl = [tex]\frac{293}{36.5}[/tex] = 8.03mole
Now we proceed to find molarity:
Molarity = [tex]\frac{8.03}{0.666}[/tex] = 12.06moldm⁻³
(b)2.026 g in 0.1250 ml of a solution used as an unknown in general Chemistry laboratory:
Given parameters:
Mass of solute = 2.062g
Volume of solution = 0.1250mL
Unkown:
Molarity of the solution
Since molarity simply expresses the amount of solute in a substance, we can also use the express below:
Molarity = [tex]\frac{mass of solute}{Volume of solution}[/tex] = [tex]\frac{2.062}{0.125}[/tex] = 16.496g/mL
(c) 0.001 mg Cd2+ in 0.100 L the maximum permissible concentration of cadmium in drinking water
Given parameters:
mass of cadmium ions = 0.001mg
Volume of solution = 0.1L
Unknown:
Molarity of the solution =?
Molarity = [tex]\frac{mass of solute}{volume of solution}[/tex] = [tex]\frac{0.001}{0.1}[/tex] = 0.01mg/L
(d) 0.0079 g C7H5SNO3 in one ounce(29.6mL), concentration of saccharin in a diet soft drink:
Given parameters:
Mass of saccharin, C₇H₅SNO₃ = 0.0079g
Volume of solution = 29.6mL
Unknown:
Molarity = ?
Molarity = [tex]\frac{mass of solute}{volume of solution}[/tex] = [tex]\frac{0.0079}{29.6}[/tex] = 0.00027g/mL
